In refinery processes, feeds such as crude oil, distillates and residual crude oil fractions generally contain contaminants which tend to deactivate catalyst for chemical conversion of the feeds. Contaminants which are especially abundant are sulphur containing compounds, such as hydrogen sulfide and sulphur containing hydrocarbons, and nitrogen containing compounds.
Hydrotreating processes are used to remove such contaminants from refinery feedstocks and generally involve contacting the hydrocarbon feed in the presence of hydrogen with a hydrotreating catalyst under hydrotreating conditions. Besides contaminants removal, further conversions can take place such as hydrocracking and aromatics hydrogenation.
Hydrotreating catalysts comprise hydrogenation metal components on an oxidic carrier. The hydrogenation metal components are generally Group VI metal component such as molybdenum and/or tungsten and Group VIII metal components such as nickel and/or cobalt. The hydrogenation metal components tend to be present as metal sulphide. The metal component can be incorporated into the carrier in the form of the sulphide but generally is converted into sulphide either by sulphiding the catalyst before operation or during start of the operation. Sulphiding the hydrotreating catalyst before it is used in operation is known as a pre-sulphidation treatment. Sulphur-containing compounds for use in pre-sulphidation treatments include mercaptans, sulphides, disulphides, polysulphides and sulphoxides.
The pre-sulphidation treatment results in hydrotreating catalysts that display increased hydrotreating activities. Hydrotreating catalysts that show an improved activity are becoming increasingly important in view of stricter environmental requirements that need to be met.
In addition to the use of a pre-sulphidation treatment organic compounds are being used to improve the activity of hydrotreating catalysts further.
In this respect reference can for instance be made to EP-A-0496592. In this patent specification a method is proposed for preparing a sulphided hydrotreating catalyst in which metals of the Group VI and the Group VIII of the Periodic Table; a carboxylic acid such as glycolic acid, citric acid or gluconic acid; and an organic sulphur compound are mixed with a carrier material, after which the mixture is kneaded, shaped and then dried.
Further, in US-A-2012/0168350, a process is described for preparing a slurry catalyst composition for use in the upgrade of heavy oil feedstock. The process comprises providing an inorganic metal precursor solution comprising at least one of a Group VIB metal precursor and a Group VIII metal precursor; mixing a polar aprotic solvent with the inorganic metal precursor solution to form an oil-dispersible inorganic metal precursor, and providing a sulphiding agent to sulphide the oil-dispersible inorganic metal precursor forming the slurry catalyst. The polar aprotic solvent is a solvent such as N-Methylpyrrolidone (NMP) and dimethylformamide (DMF).
US-A-2012/0145600 describes a process for preparing solutions for use in catalyst preparation which solutions are formed by bringing together in an aqueous medium i) at least one phosphorus compound, ii) at least one Group VI metal compound, iii) at least one Group VIII metal compound and iv) one or more specific ethylene glycols. An organic acid is optionally included.
Object of the present invention is to provide a process for preparing a sulphided catalyst displaying an improved hydrotreating activity.